1. Field of the Invention
The present invention generally relates to aiming, guiding, and hole forming for surgical procedures, and more particularly to a method and apparatus for determining coaxial alignment between fasteners and holes in a device which has been located within a bone.
2. Discussion of the Related Art
It is well known that many damaged and broken bones are repaired by the insertion by an intramedullary rod or pin. Also known as osteosynthesis aids, these rods or pins facilitate connection of the bone pieces together and are usually placed in the long axis of the damaged bone. If the bone is broken into two or more parts the rod stabilizes and secures the bone parts relative to each other to aid in proper healing and it also supports the bone during the healing process. Such a rod can have one, or more, holes drilled perpendicular to its longitudinal axis to allow fasteners to be inserted through the bone and into the rod to fix the rod""s location in the bone. In many instances holes must be drilled, or otherwise formed, in the bone before fasteners can be inserted through the bone and into the transverse rod holes. Of course, it is not possible to see the hole, or holes, in the rod once the rod has been inserted within the bone, so X-ray means are used to view the rod through the bone and determine where the transverse holes are located in the intramedullary rod.
Once the transverse intramedullary rod holes are found and their orientation is determined, a matching hole or set of holes must be formed in the bone. It is vital that holes formed in the bone and their matching rod holes are coaxially aligned. This coaxial alignment results in fasteners that are concentrically aligned with the rod holes, which assures that the fasteners indeed engage the rod holes and that the bone parts are not twisted or misaligned relative to each other when the fastener is inserted in the rod.
Aiming devices for coaxial bone hole formation are known in the art. They include spaced rings and wires which help the doctor determine the correct coaxial alignment for the hole, or holes, to be drilled in the bone. A source of X-ray radiation is arranged on one side of the procedure area, with an X-ray receiver on the other side. The doctor views the fractured bone, intramedullary rod, and aiming device through a X-ray imaging screen. The doctor then uses such an aiming device to determine the correct location and orientation for the holes to be drilled in the bone.
One of the problems encountered during the procedure is that once the correct orientation and location of the hole to be drilled in the bone has been found, the alignment device may drift on the slick bone surface or otherwise lose the correct orientation from contact with surrounding soft tissue and therefore the resulting hole is no longer optimally aligned. Additionally, if a drill is used to drill a hole through the bone, the drill can slip from the desired location and the resulting hole will be misaligned. Moreover, the drill must be maintained at the desired orientation throughout the drilling procedure, or else the resulting hole will not be coaxially aligned with the rod hole.
The present invention solves the problem of undesirable movement during a procedure with a cannulated system that allows for quick and accurate coaxial alignment with transverse holes located in a rod. Also, the invention allows for accurate location of a drill, accurate guiding of the drill, and also accurate guidance for fasteners, which are inserted through the bone and into the transverse holes.
Broadly, the present invention concerns a method and apparatus for determining and maintaining coaxial alignment with transverse intramedullary rod holes. More specifically, one embodiment of the invention uses a radiographic pin centrally mounted in a cylindrical it radiolucent plug, the plug being slidably engaged in a cannula, or guide sleeve, having a sharp edge which is placed against a bone. Using X-ray means, the pin is used to coaxially align the cannula with the transverse intramedullary rod hole, and then the sharp edge of the cannula is driven into the bone sufficiently to make an impression, establishing a guide sleeve position that is properly oriented throughout a medical procedure. The pin is also driven into the bone, creating an indentation that acts as a pilot-hole, or marking point, for a drill which is inserted in the guide sleeve after the pin and plug assembly is removed. The drill uses the sleeve as a guide to ensure proper coaxial alignment with the rod hole. Once a hole is drilled the drill is removed from the guide sleeve and a fastener is inserted in the sleeve. Again, the sleeve is used as a guide to ensure proper alignment of the fastener into the bone and into the transverse hole in the rod.
The invention affords its users with a number of distinct advantages. Unlike prior alignment systems, the present invention uses a cannulated system to secure a guide sleeve firmly against the bone which allows for an alignment, once determined, to remain accurate throughout the procedure. Also, a guide pin is used to create an indentation, or mark, in the bone which acts as a starting point and guide for the drilling operation. Additionally, the sleeve system guides the drill for its drilling operation, and also guides the fastener. Thus, the aiming and guiding apparatus according to the invention not only quickly and accurately determines proper coaxial alignment, but it assures correct alignment throughout the medical procedure.